1. Field of the Invention
The invention relates to a technique for correcting optical characteristics of a lens by image processing.
2. Description of the Related Art
As a correction of image deterioration due to optical characteristics, a correction value is ordinarily calculated based on information from a lens unit. The information can include a shooting distance, a focal length, and an aperture value, and the like, and the correction value is calculated from the information for correction. An image without aberration and distortion caused by the optical characteristics can be obtained by the correction (see Japanese Patent Application Laid-Open No. 5-158134).
Further, when an intermediate adaptor, such as an extender and the like, is interposed into an interchangeable lens unit of a single-lens reflex camera, an aperture value of the lens unit may not indicate a correct value. To cope with the above issue, the camera can include length information of the intermediate adaptor and an aperture value correction table corresponding to an exit pupil distance (see Japanese Patent Application Laid-Open No. 2007-17891).
However, the optical characteristics of a lens unit may not be specified even based on the shooting distance, focal length, and aperture value. For example, there may be a case where a shooting magnification to a change of a shooting distance does not correspond to a change of the shooting distance in the relation of 1:1, as occurring in a macro lens. When the optical characteristics are corrected based on a lens position using information corresponding to a shooting distance, an erroneous correction may be performed.